Monitoring Geothermal Flow at the Lightning Dock Geothermal Area, New Mexico Using Long-Duration Passive Seismic Imaging

Abstract

Monitoring subsurface fluid flow is crucial for optimizing geothermal energy production. The Lightning Dock Geothermal field (LDG) is located on the east side of Animas Valley in Hidalgo County, New Mexico, USA. LDG geothermal wells produce from fractures within the intersection of buried normal faults, as revealed by drilling and previous seismic traveltime tomography and gravity inversion. During July to August, 2020, Zanskar deployed a large-N nodal array consisting of 1,206 seismic geophones centered around the LDG production and injection region to acquire continuous passive seismic data. We first update the velocity model using an adjoint-state first-arrival traveltime tomography using several borehole string shot data acquired at LDG. We then apply a frequency-domain full-wavefield passive seismic imaging method to the acquired long-duration passive seismic data to image the subsurface fluid-flow pathways at LDG and their temporal changes. Our tomography and passive imaging results reveal high-resolution time-lapse geothermal fluid pathway images at LDG. We analyze the temporal-spatial relationships between the imaged flow pathways and geothermal production activities at LDG using these imaging results. Our imaging results provide valuable information for understanding the geothermal resource and current fluid pathways and siting new wells at LDG.